Analysis And Construction On The Fine Structure Of Regional Geoid

The determination of geoids is an important part of earth science research,and it is also a hot topic in geodetic studies today.The use of GNSS positioning technology,leveling techniques,and the determination theory and methods of modern Earth's gravitational field to establish a high-precision,high-resolution region-like geoid,is of great scientific importance.This paper first introduces the basic concepts of the construction of regional geoids and several methods for the refinement of geoids.It compares and analyzes the differences between four gravity field models and precision leveling data,and aims at the actual refinement of geoids in complex regions.The problems existing in the analysis of the fine structure of the regional geoids explore the relevant theories and methods for constructing more accurate geoids.The main research content of this paper is as follows:(1)The quasi-geolevels calculated by the four gravity field models ITU_GRACE16,GOCO05 C,EIGEN-6C and EGM2008 in the 40°N-42.5°N and 113°E-115.5°E regions are introduced.Using the elevation anomaly calculated from the GNSS level data,the EGM2008 model has the highest accuracy in this area.(2)Taking the application of the EGM2008 model in this area as an example,three different resolutions are used to calculate the elevation anomaly of the area.It was determined that constructing a centimeter-level provincial region like a geoid using a spatial resolution of 10??×10? does not meet the requirement and requires the use of higher resolution spatial data.Therefore,this paper uses 1?×1? spatial resolution mesh data as the analysis object.(3)This paper uses slope method to calculate and analyze the fine structure of regional geoid.Eight grids were used to calculate and analyze the grid data,and the changes of the geoid fluctuations in the region were obtained.To further refine the geoid,the area is divided into a gently rolling northwest region and a more fluctuating southeast region.Then use polynomial fitting method,multi-surface function method,thin plate spline method,and BP neural network model for example calculation analysis,and use the removal-recovery method to analyze the pros and cons of the fitted model.(4)Finally,the virtual spherical harmonic method was used to reconstruct the geoid,and the radius of the spherical cap in Jiangxi Province was selected as the experimental object.The geoid data was calculated using the EGM2008 model as the observed value,which was determined by the geoid fine structure analysis results.With the increased virtual boundary value,an approximation experiment is performed by adding a width transition zone outside the spherical cap boundary to calculate high-precision and high-resolution regional geoids.The new model can be built on the provincial scale with an accuracy of up to centimeters level.